FIELD OF THE INVENTION
The present invention relates to an ultrasonic bonding wheel assembly for cutting and sealing both sealable fabrics and tape material. In yet another aspect of the invention is the method for sealing sheetlike materials without bonding holes through the seam.
The present invention concerns an ultrasonic seaming apparatus in which vibratory energy in the sonic or ultrasonic frequency range is used for welding or fusing together two superposed flexible sheet materials by passing such materials between a anvil and the output surface of a resonating horn. An apparatus of this type is particularly suited for seaming thermoplastic sheets or textile materials made entirely of thermoplastic fibers and is known also as an "ultrasonic sewing machine", although no needle and thread are used for providing a seam.
Unique problems present themselves when a seaming apparatus of this type is used for seaming sheer material, for instance curtain material. Upon feeding such material through the seaming station between the resonating horn and the anvil, puckering occurs which adversely affects the appearance, quality, and sales appeal of the seamed article. It has been found that such puckering can be minimized, if not totally eliminated, if a special feed wheel is provided which is disposed for engaging the workpiece immediately after its emergence from the seaming station, pulling the workpiece away from such station. Therefore, the present invention concerns the provision of a workpiece feeding wheel designed and mounted in such a way that it is urged toward contact with the periphery of the rotating anvil wheel and engages the respective workpieice portion immediately after the passage thereof between the anvil wheel and the frontal surface of the resonating horn. Means are present for diving the anvil wheel and the workpiece feed wheel at coordinated peripheral speeds.
A still other object of the present invention concerns the construction of an ultrasonic seaming apparatus which is provided with a workpiece immediately after its passage through the seaming station.
A further object of this invention is the provision of an ultrasonic seaming apparatus which includes a seaming station comprising a rotatable anvil wheel and a resonating horn mounted for providing ultrasonic energy to a workpiece which is fed between the frontal surface of the horn and the anvil, a workpiece feed wheel disposed for engaging the workpiece, means for urging the workpiece feed wheel toward contact with the anvil wheel, and drive means coupled for driving the anvil wheel and the workpiece feed wheel at correlated peripheral speeds.
The present apparatus discloses a seaming and cutting apparatus of this type in which ultrasonic means are provided to effect a longitudinal seam and additional means are provided to simultaneously cut and fuse the material adjacent the seamed are without that excessive wear is manifest at the instrumentality providing such cutting action. In this manner it is possible to fabricate completely finished articles, such as curtains or spreads, wherein the folded seam or hem usually deemed necessary to provide an acceptable finished appearance can be omitted. Moreover, the cutting instrumentality operable in conjunction with the seaming apparatus is constructed so as to eliminate excessive wear by being resiliently mounted relative to the frontal surface of the horn which provides the mechanical energy for cutting. A further salient feature of the invention concerns an arrangement for adjusting the cutting action with regard to pressure and bringing unused cutting edge portions into operative position.
More recently the need has arisen for a seaming machine which ultrasonically fuses or bonds two or more layers of thermoplastic material together in a manner similar to a sewing machine and includes means for cutting and fusing the material in a marginal portion adjacent the seam.
In various industries, it is necessary for certain employees and others to be in close proximity to hazardous chemicals and others hazardous matter. Local, state, and federal laws and/or regulations often require the use of protective garments under such circumstances. It is frequently not feasible to utilize "permanent" protective garments because of the necessity to decontaminate the garments regularly, which may be impossible or prohibitively expensive. A widely used alternative to such permanent protective garments is the disposable garment, made of man-made materials which are lightweight, resistant to tearing and abrasion, and relatively impermeable to hazardous substances. Such synthetic fabrics are available, such as spunbounded olefin, which are very satisfactory. They are good barriers to particulates and a broad range of chemicals, have high tensile strength and tear resistance, and are reasonably economical. An example of this synthetic fabric is sold by E.I. du Pont de Nemours & Co. under its trademark Tyvek, to which may be added a polyethylene or polyvinylidine chloride film coat or lamination on one of its two sides to make it even more impervious to hazardous substances.
A technical problem in using such synthetic fabrics is how to form garments therefrom without significant loss of the favorable properties of the fabrics. In virtually all instances, a stitching process issued in whole or in substantial, a stitching process is used in whole or in substantial part to form garments from such synthetic materials so that they will conform generally to the shape of the human body. However, the stitching process obviously results in the creation of many holes in the fabric which are points of vulnerability through which hazardous gases, liquids and some small solid particulates can penetrate, with possible damage to the body or inner clothing, or both, of the person wearing the protective garment. It is thus desirable to minimize to the extent possible the use of traditional stitching methods which create such vulnerable holes.
One patent, Goldstein U.S. Pat. No. 4,272,851, attempts to solve this problem by ultrasonically bonding together edges of synthetic fabric, preferably polyethylene coated (laminated) Tyvek. However, Goldstein suggests the ultrasonic bonding of congruent edges of the Tyvek, presumably laminated side to laminated side. This procedure results in a seam which has inadequate resistance to rupture from shearing. In order to give greater strength against shear stresses, Goldstein adds a binding along the folded back seam, which binding is sewed on by traditional stitching means. While the multiple layers so stitched may be somewhat more protective than earlier stitching methods, it is still possible for hazardous chemicals and substances to get inside the garment through the holes created by sewing.